As an example of a mobile communication system to which the present invention is applicable, a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) or LTE-advanced (hereinafter, LTE-A) communication system will be schematically described.
One or more cells may exist per eNB. The cell is set to use a bandwidth such as 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz or 20 MHz to provide a downlink or uplink transmission service to several UEs. Different cells may be set to provide different bandwidths. The eNB controls data transmission or reception of a plurality of UEs. The eNB transmits downlink (DL) scheduling information of DL data so as to inform a corresponding UE of time/frequency domain in which data is transmitted, coding, data size, and Hybrid Automatic Repeat and reQuest (HARQ)-related information. In addition, the eNB transmits uplink (UL) scheduling information of UL data to a corresponding UE so as to inform the UE of a time/frequency domain which may be used by the UE, coding, data size and HARQ-related information. An interface for transmitting user traffic or control traffic can be used between eNBs.
Although radio communication technology has been developed up to Long Term Evolution (LTE) based on Wideband Code Division Multiple Access (WCDMA), the demands and the expectations of users and providers continue to increase. In addition, since other radio access technologies have been continuously developed, new technology evolution is required to secure high competitiveness in the future. Decrease in cost per bit, increase in service availability, flexible use of a frequency band, simple structure, open interface, suitable User Equipment (UE) power consumption and the like are required.
Recently, the standardization of the subsequent technology of the LTE is ongoing in the 3GPP. In the present specification, the above-described technology is called “LTE-Advanced” or “LTE-A”. The LTE system and the LTE-A system are different from each other in terms of system bandwidth and introduction of a relay node.
The LTE-A system aims to support a wideband of a maximum of 100 MHz. The LTE-A system uses carrier aggregation or bandwidth aggregation technology which achieves the wideband using a plurality of frequency blocks. Carrier aggregation enables a plurality of frequency blocks to be used as one large logical frequency band in order to use a wider frequency band. The bandwidth of each of the frequency blocks may be defined based on the bandwidth of a system block used in the LTE system. Each frequency block is transmitted using a component carrier.
In an LTE-A system, although a relay node has been introduced for the purpose of expanding cell coverage, complementing a shadow area, and improving throughput of a cell boundary, the relay node may not simultaneously transmit and receive a signal via an access link and a backhaul link. However, such a problem has not been solved.